President Joko Widodo has called for calm after reports that tainted rice may have caused the hospitalisation of a girl in Medan on Sunday and made some customers at a food market in Bekasi sick last week.

Rice is a common food staple in Indonesia, the world's third biggest importer, and reports of contamination can quickly cause food scares in the vast archipelago.

"The synthetic rice distributor ... may be making an attempt at treason or trying to sabotage the government," Home Minister Tjahjo Kumolo was quoted as saying by the English-daily Jakarta Post.

The scare began last week when customers complained of nausea and dizziness after eating suspect rice from a vendor in Bekasi, a town neighbouring the capital of Jakarta.

Initial tests indicated the rice was contaminated with plastic and plastic softeners.

Indonesia elections: Jokowi versus Prabowo

Widodo, however, urged consumers to wait for official government test results before jumping to conclusions.

"Don't everyone just talk and make the problem bigger," Widodo told reporters on Sunday as quoted by online news site Detik.com. "What is most important is to look at the root problem and check if it really was in Bekasi or just one vendor."

Police were waiting for the results of official tests before continuing their investigation, Assistant Police Commissioner Siswo told Reuters.